Transient dynamic analyses involving large deformations or large rotations exhibit significant changes in stiffness and inertia properties. The default response-frequency-based automatic time-stepping criterion may not be suitable for such nonlinear analyses. Use the MIDTOL command to automatically adjust the time increment based on convergence at the middle of the substep and convergence at the end of the substep. For more information, see Nonlinear Structural Analysis in the Structural Analysis Guide.